Organic pigment nanoparticle thin film devices via Lewis acid pigment solubilization and in situ pigment dispersions are described by Hsieh, B. R.; Melnyk, A. R., Xerox Corporation, Webster, N.Y., U.S.A., in the Journal of Imaging Science and Technology 45(1), 37-42 [2001].
A number of patents describe processes for the preparation of nanosize pigments. For example, U.S. Pat. No. 5,679,138 describes a process for the preparation of ink jet inks comprising pigments with a pigment particle size of less than 100 nanometers prepared by milling the corresponding pigments in a high speed mill and its use for ink jet printers. EP-1,195,413 describes the production of finely divided organic pigments by precipitation in a micro jet reactor, with the resulting pigment suspension being removed by a gas or vaporized liquid. An example is given which provided copper tetrachloro phthalocyanine having an average partide size of 26±11 nm.
U.S. Pat. No. 6,225,472 and U.S. Pat. No. 6,406,533 describe 6,13-dihydroquinacridone derivatives that can direct and control the growth and/or crystal phase of pigment partides.
U.S. Pat. No. 6,264,733 describes new pigment particle growth and/or crystal phase directors of formula (MO3S)m-Q-(CH2—(X)—(Y)n)o(I), wherein Q represents a pigment moiety, M represents a metal cation, quatemary N cation or H, X is a aromatic group or a cyclo-hetero aliphatic group with at least one 5 atom or 6 atom ring or a hetero aromatic group with at least one 6 atom ring and which is not a phthalimido group, Y is a sulfonic acid or carboxylic acid or salt thereof; m and n independent of each other represent an integer from zero to 2.5; and o is an integer from 0.05 to 4.
Although such compounds can effectively direct the growth and crystal phase of pigment particles when present during the pigment synthesis, they have the disadvantage of being a pigment derivative and therefore need to be separately synthesized first and are subject to additional regulatory clearances.
The state of the art literature does not describe the use of nanosize pigment particles to induce pigment crystal growth or as crystal phase directors during pigment synthesis or pigment finishing.